Java中feign的独立使用

独立应用feign能够帮助我们解决什么样的问题或者带来什么好处呢。一方面是优雅，优雅的代码总是具有更好的可读性,这将意味着可能具有更好的维护性。另一方面是独立,独立意味着它可以不依赖繁琐的框架,意味着能够在更多的环境中得到应用。

1、建立一个基于maven的普通的Java项目,pom.xml配置如下

<dependencies><dependency><groupId>io.github.openfeign</groupId><artifactId>feign-core</artifactId><version>9.7.0</version></dependency><dependency><groupId>io.github.openfeign</groupId><artifactId>feign-gson</artifactId><version>9.7.0</version></dependency>
</dependencies>

2、使用到的一些注解

FeignService.java

package com.suntown.annotation;import java.lang.annotation.*;@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface FeignService{}

Url.java

package com.suntown.annotation;import java.lang.annotation.*;@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Url{public String value();
}

Wired.java

package com.suntown.annotation;import java.lang.annotation.*;@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Wired{}

3、自动扫描package并管理feign接口类

FeignJust.java

package com.suntown;import com.suntown.annotation.FeignService;
import com.suntown.annotation.Url;
import com.suntown.annotation.Wired;
import feign.Feign;
import feign.Request;
import feign.Retryer;
import feign.gson.GsonDecoder;
import feign.gson.GsonEncoder;
import sun.net.www.protocol.file.FileURLConnection;import java.io.File;
import java.io.FilenameFilter;
import java.io.IOException;
import java.lang.reflect.Field;
import java.net.JarURLConnection;
import java.net.URISyntaxException;
import java.net.URL;
import java.net.URLConnection;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Map;
import java.util.jar.JarEntry;
import java.util.jar.JarFile;public class FeignJust{private static Map<Class,Object> actionMap = new HashMap<>();private static Map<Class,Object> feignServiceMap = new HashMap<>();public static <T> T getAction(Class<T> interClass){return (T) actionMap.get(interClass);}public static <T> T action(Class<T> tClass,String url){T action = Feign.builder().encoder(new GsonEncoder()).decoder(new GsonDecoder()).options(new Request.Options(1000, 3500)).retryer(new Retryer.Default(5000, 5000, 3)).target(tClass,url);return action;}public static String firstLower(String s){return (char)(s.charAt(0) + 32) + s.substring(1);}public static void scanPackage(String packageName) {try {String packageNamePath = packageName.replace(".","\\");URL url = FeignJust.class.getResource("FeignJust.class");URLConnection urlConnection = url.openConnection();if(urlConnection instanceof FileURLConnection){FileURLConnection fileURLConnection = (FileURLConnection)urlConnection;File rootFile = new File(FeignJust.class.getResource("/").toURI().getPath());File dirFile = new File(rootFile.getAbsolutePath() + File.separator + packageNamePath);File[] classesFile = dirFile.listFiles(new FilenameFilter() {@Overridepublic boolean accept(File file, String s) {return s.endsWith(".class");}});for(File classFile : classesFile){String classFilePath = classFile.getAbsolutePath();String className = classFilePath.substring(rootFile.getAbsolutePath().length() + 1).replace("\\",".");className = className.substring(0,className.length() - 6);Class interClass = FeignJust.class.getClassLoader().loadClass(className);Url urlAno = (Url)interClass.getAnnotation(Url.class);if(urlAno!=null){Object action = FeignJust.action(interClass,urlAno.value());String classSimpleName = firstLower(interClass.getSimpleName());actionMap.put(interClass,action);}}}else if(urlConnection instanceof JarURLConnection){JarURLConnection jarURLConnection = (JarURLConnection)urlConnection;URL jarFileURL = jarURLConnection.getJarFileURL();File fileJarFile = new File(jarFileURL.toURI().getPath());JarFile jarFile = jarURLConnection.getJarFile();Enumeration<JarEntry> it = jarFile.entries();while(it.hasMoreElements()){String className = it.nextElement().getName().replace("/",".");if(className.endsWith(".class") && className.startsWith(packageName + ".")){className = className.substring(0,className.length() - 6);Class interClass = FeignJust.class.getClassLoader().loadClass(className);Url urlAno = (Url)interClass.getAnnotation(Url.class);if(urlAno!=null){Object action = FeignJust.action(interClass,urlAno.value());String classSimpleName = firstLower(interClass.getSimpleName());actionMap.put(interClass,action);}}}}} catch (IOException e) {e.printStackTrace();} catch (URISyntaxException e) {e.printStackTrace();} catch (ClassNotFoundException e) {e.printStackTrace();}}public static <T> T getService(Class<T> interClass) {return (T) feignServiceMap.get(interClass);}public static void scanServicePackage(String packageName) {try {String packageNamePath = packageName.replace(".","\\");URL url = FeignJust.class.getResource("FeignJust.class");URLConnection urlConnection = url.openConnection();if(urlConnection instanceof FileURLConnection){FileURLConnection fileURLConnection = (FileURLConnection)urlConnection;File rootFile = new File(FeignJust.class.getResource("/").toURI().getPath());File dirFile = new File(rootFile.getAbsolutePath() + File.separator + packageNamePath);File[] classesFile = dirFile.listFiles(new FilenameFilter() {@Overridepublic boolean accept(File file, String s) {return s.endsWith(".class");}});for(File classFile : classesFile){String classFilePath = classFile.getAbsolutePath();String className = classFilePath.substring(rootFile.getAbsolutePath().length() + 1).replace("\\",".");className = className.substring(0,className.length() - 6);Class interClass = FeignJust.class.getClassLoader().loadClass(className);FeignService feignService = (FeignService)interClass.getAnnotation(FeignService.class);if(feignService!=null){Object serivce = FeignJust.serivce(interClass);String classSimpleName = firstLower(interClass.getSimpleName());if(serivce!=null){Field[] fields = interClass.getDeclaredFields();for(Field field : fields){if(field.getAnnotation(Wired.class)!=null){field.setAccessible(true);Object action = getAction(field.getType());if(action!=null){field.set(serivce,action);}}}feignServiceMap.put(interClass, serivce);}}}}else if(urlConnection instanceof JarURLConnection){JarURLConnection jarURLConnection = (JarURLConnection)urlConnection;URL jarFileURL = jarURLConnection.getJarFileURL();File fileJarFile = new File(jarFileURL.toURI().getPath());JarFile jarFile = jarURLConnection.getJarFile();Enumeration<JarEntry> it = jarFile.entries();while(it.hasMoreElements()){String className = it.nextElement().getName().replace("/",".");if(className.endsWith(".class") && className.startsWith(packageName + ".")){className = className.substring(0,className.length() - 6);Class interClass = FeignJust.class.getClassLoader().loadClass(className);Url urlAno = (Url)interClass.getAnnotation(Url.class);if(urlAno!=null){Object action = FeignJust.action(interClass,urlAno.value());String classSimpleName = firstLower(interClass.getSimpleName());actionMap.put(interClass,action);}}}}} catch (IOException e) {e.printStackTrace();} catch (URISyntaxException e) {e.printStackTrace();} catch (ClassNotFoundException e) {e.printStackTrace();} catch (IllegalAccessException e) {e.printStackTrace();}}private static Object serivce(Class interClass) {try {return interClass.newInstance();} catch (InstantiationException e) {e.printStackTrace();} catch (IllegalAccessException e) {e.printStackTrace();}return null;}
}

4、测试接口类 IBaseAction.java

package com.suntown.interaction;import com.suntown.annotation.Url;
import feign.Headers;
import feign.RequestLine;@Url("http://localhost:8089")
public interface IBaseAction{@RequestLine("POST /login/login")@Headers({"Content-Type: application/json","Accept: application/json"})public Object login(Admin admin);public static class Admin{private String username;public String getUsername() {return username;}public void setUsername(String username) {this.username = username;}public String getPassword() {return password;}public void setPassword(String password) {this.password = password;}private String password;}
}

5、feign接口的调用

package com.suntown;import com.suntown.interaction.IBaseAction;public class Main{public static void main(String[] args){FeignJust.scanPackage("com.suntown.interaction");IBaseAction baseAction = FeignJust.getAction(IBaseAction.class);IBaseAction.Admin admin = new IBaseAction.Admin();admin.setUsername("admin");admin.setPassword("123");Object result = baseAction.login(admin);System.out.println("class="+result.getClass()+","+result);}
}

6、运行结果

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